Factor analysis of Carpal Tunnel Syndrome Questionnaire in relation to nerve conduction studies

doi:10.1016/j.clinph.2011.02.030

Clinical Neurophysiology

Volume 122, Issue 10, October 2011, Pages 2067-2070

https://doi.org/10.1016/j.clinph.2011.02.030 Get rights and content

Abstract

Objective

This study aims to assess the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) structure and its relation to nerve conduction studies (NCS).

Methods

A total of 403 patients with clinical and/or electrophysiological definition of CTS were evaluated with the instrument. The structure of the questionnaire was assessed by means of factor analysis. Factors obtained were compared with NCS.

Results

Factor analysis showed that three factors represented nearly 60% of the variance of the instrument. Factor one is related to all the function domain questions and to the weakness and difficulty in grasping questions of the symptom domain; factor two to questions that assess numbness and tingling, and to the pain-awakening question of the symptom domain; and factor three, to pain questions of the symptom domain. Factor two had a stronger correlation with latencies of NCS and with the neurophysiological scale than the other two factors.

Conclusions

BCTQ assesses function and symptoms in patients with CTS by means of questions related to numbness and tingling sensation, pain and functional status. Questions related to numbness and tingling (factor two) better reflected the pathophysiology of the median nerve.

Significance

Factor-2 sensory-related questions of BCTQ may be more useful in diagnosis, follow-up and assessing therapeutic outcome in CTS.

Highlights

► Based on factor analysis, the variance of Boston Carpal Tunnel Syndrome Questionnaire can be represented by three separate factors: functional status (factor one), sensory symptoms (factor two) and pain (factor three). ► Questions relating to numbness and tingling (factor two) had a strong and direct statistical correlation with sensory and motor distal latencies of the median nerve. ► Questions related to sensory symptoms are most useful to determine the severity of disease of Carpal Tunnel Syndrome and to evaluate outcomes.

Introduction

Carpal Tunnel Syndrome (CTS) is a common complaint in primary setting with 4% estimated prevalence in general population (Atroshi et al., 1999). Diagnosis relies on clinical examination and nerve conduction studies (NCS), although these studies are not essential for CTS case definition. In addition to an accurate diagnosis, it is important to know the severity of CTS, which is based on NCS and clinical scales. Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) is a patient-perception-of-disease scale, which assesses the severity of hand symptoms and the functional impairment in both clinical and epidemiological scenarios (Levine et al., 1993). The questionnaire has shown reliability and sensitivity to change and has been validated in several languages. It has also been used as a tool for assessing the effect of different treatments on CTS. Nevertheless, factor structure (which is part of construct validity) has not been completely examined (Leite et al., 2006). Factor analysis is a statistical method that analyzes relationships among variables (i.e. questions of a questionnaire) and how these variables belong to a common underlying dimension (factor). Each dimension may be evaluated separately and its validity may be compared with some other variable (i.e. NCS).

Factor analysis is a statistical method that has been used in the study of many neuromuscular diseases. It has taken part, for example, in the assessment of internal consistency of functional scales of patients with motor neuron disease (Cedarbaum et al., 1999, Campos et al., 2010), as well as in the assessment of relevant complaints in patients with diabetic polyneuropathy and its relation with neurophysiological abnormalities (Valk et al., 1994). In CTS, factor analysis has been used to differentiate and classify symptoms (You et al., 1999).

The objective of this study was to evaluate the factor structure (different factors) underlying the BCTQ and its relation to nerve conduction studies (NCS). We hypothesize that the factor structure of BCTQ may identify those questions that are more relevant for diagnosis of CTS.

Section snippets

Materials and methods

Subjects were recruited from patients referred to the Laboratory of Neurophysiology at Clínica Carlos Lleras Restrepo, Bogotá – Colombia, from March 2005 to March 2006, who were under suspicion of CTS. The study was approved by the Committee on Clinical Research, School of Medicine, Universidad Nacional de Colombia. Before NCS, all patients were interviewed with the BCTQ Spanish version. The questionnaire comprises 19 questions that assess two domains, namely functional impairment and severity

Demographic characteristics of patients are shown in Table 1

Kaiser–Meyer–Olkin (KMO) was 0.91, which suggests that variables are correlated and factor analysis is appropriate for our data. Electrophysiological variables and BCTQ scores did not show a normal distribution. Factor analysis shows that the most appropriate approach is to use three factors. Less than three factors would represent a small part of the variance and more would not represent a parsimonious analysis (one of the conditions of factor analysis is that phenomena must be explained with

Discussion

This study shows that the variance of BCTQ could be represented by three separate factors that could be roughly divided into questions related to functional status (factor one), sensory symptoms (factor two) and pain (factor three). The correlation of BCTQ with NCS (criterion validity) for sensory and motor NCS is different for each domain. The evidence is that questions related to numbness and tingling (factor two) from the symptom domain had a strong and direct statistical correlation with

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They also proposed that numbness, tingling, and nocturnal paresthesia are main symptoms in CTS and appear to be more closely related to peripheral nerve lesions as opposed to pain which is a symptom associated with more musculoskeletal or joint disease. They also found no statistical correlation between pain and nerve conduction studies (Ortiz-Corredor et al., 2011). de la Llave-Rincón et al. detected no significant differences in pain parameters among patients with minimal, moderate, and severe CTS.
To evaluate the link between EMG findings and clinical status, the Boston questionnaire and the severity of pain in patients with pre-diagnosis of carpal tunnel syndrome.
A total of 85 patients (133 hands) who presented to the Physical Therapy and Rehabilitation outpatient clinic consecutively with complaints of numbness, tingling, pain and weakness in their hands were evaluated for their demographic and clinical features. After the initial evaluation, the diagnosis of CTS was confirmed by EMG. Visual analog scale (VAS), the Boston Questionnaire (Symptom Severity Scale = SSS, Functional Status Scale = FSS) and nerve conduction study results (sensory conduction velocity = SCV, distal motor latency = DML, compound muscle action potential = CMAP) were enrolled.
Eighty-five patients (58 female and 27 male) participated in this study yielding 133 hands (73 right hands, 60 right hands) with CTS. The mean age was 48.3 ± 10.41 years. Of all patients, 68.2 % were female and 31.8 % were male. A statistically significant relationship was found between SSS and duration of symptoms, VAS, both right and left SCV, DML and CMAP. A statistically significant relationship was found between FSS and duration of symptoms, VAS and only right SCV, DML and CMAP.
The diagnosis of CTS should be evaluated not only as an electrodiagnostic finding, but also the clinical picture of the patients. According to our results, both SSS and FSS had good correlations with VAS and the findings of EMG. Therefore, the Boston Questionnaire can provide a standardized measure of symptom severity and functional status in patients with CTS.
Predominant patterns of median nerve displacement and deformation during individual finger motion in early carpal tunnel syndrome
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A higher SSS score suggests more serious symptoms, and a higher FSS score implies more critical functional interference (Impink et al. 2011). The BCTQ has been used in previous studies (Impink et al. 2011; Martins et al. 2008) and was chosen because of its high reproducibility, validity and sensitivity to any clinical changes (Meirelles et al. 2006; Ortiz-Corredor et al. 2011). According to the BCTQ, symptomatic individuals have scores greater than one on the SSS or FSS, or both; asymptomatic individuals have scores of one on scales.
Idiopathic carpal tunnel syndrome (CTS) is a common neuropathy, yet the pathologic changes do not explain the fleeting dynamic symptoms. Dynamic nerve-tendon interaction may be a contributing factor. Based on dynamic ultrasonographic examination of the carpal tunnel, we quantified nerve-tendon movement in thumb, index finger and middle finger flexion in normal subjects and those with mild-idiopathic CTS. Predominant motion patterns were identified. The nerve consistently moves volar-ulnarly. In thumb and index finger flexion, the associated tendons move similarly, whereas the tendon moves dorsoradially in middle finger flexion. Nerve displacement and deformation increased from thumb to index finger to middle finger flexion. Predomination motion patterns may be applied in computational simulations to prescribe specific motions to the tendons and to observe resultant nerve pressures. By identification of the greatest pressure-inducing motions, CTS treatment may be better developed. Symptomatic subjects displayed reduced nerve movement and deformation relative to controls, elucidating the physiologic changes that occur during mild CTS.
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Few studies evaluating CTS provide sufficient description of case definitions to allow for differentiation between symptoms in ≥1 and ≥2 median nerve–served digits. Most published case definitions of CTS in peer-reviewed research rely on combinations of symptoms in ≥1 of multiple areas, including the fifth digit (not normally innervated by the median sensory nerve) and the hand and wrist.51-53 Analysis of a subset of data where sites reported pain or burning independently of numbness or tingling was performed to evaluate differences in estimated prevalence when including pain or burning as a symptom criteria.
To analyze differences in carpal tunnel syndrome (CTS) prevalence using a combination of electrodiagnostic studies (EDSs) and symptoms using EDS criteria varied across a range of cutpoints and compared with symptoms in both ≥1 and ≥2 median nerve–served digits.
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None.
CTS prevalence was estimated while varying the thresholds for median sensory latency, median motor latency, and transcarpal delta latency difference. EDS criteria examined included the following: median sensory latency of 3.3 to 4.1 milliseconds, median motor latency of 4.1 to 4.9 milliseconds, and median-ulnar sensory difference of 0.4 to 1.2 milliseconds. EDS criteria were combined with symptoms in ≥1 or ≥2 median nerve–served digits. EDS criteria from other published studies were applied to allow for comparison.
CTS prevalence ranged from 6.3% to 11.7%. CTS prevalence estimates changed most per millisecond of sensory latency compared with motor latency or transcarpal delta. CTS prevalence decreased by 0.9% to 2.0% if the criteria required symptoms in 2 digits instead of 1.
There are meaningful differences in CTS prevalence when different EDS criteria are applied. The digital sensory latency criteria result in the largest variance in prevalence.
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All answers are rated from 1 to 5 scales, where higher scores imply more severe symptoms or greater functional impairment.20 The validity, internal consistency, and reproducibility of BCTQ have been demonstrated previously.21,22 In this study, we used a Persian version of BCTQ, which has been validated recently.23
Randomized controlled trial.
Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy of the upper extremity. To date, no previous study has evaluated the efficacy of topical Lavendula stoechas (Lavender) oil in CTS patients.
To investigate the effectiveness of topical Lavender essential oil in pain intensity, isometric pinch strength, electrophysiological features, and functional status of patients with mild to moderate CTS.
Forty eight patients with mild to moderate CTS were enrolled in this randomized placebo-controlled trial. Group A was treated with night wrist orthotic and topical lavender oil ointment. Group B was treated with night wrist orthotic and a placebo ointment. Patients were evaluated at baseline, and after 40 days of intervention with Boston CTS questionnaire (BCTQ), visual analog scale (VAS) for pain, pinch grip strength, power grip, median compound motor action potential latency, and median sensory nerve action potential latency.
At the end of the study period, both groups improved significantly in terms of BCTQ, VAS, isometric pinch powers, and electrodiagnosis study parameters. However, group A showed significantly greater improvements in BCTQ (mean difference, 0.39 ± 0.31 vs 0.6 ± 0.35; P = .03), VAS (3.37 ± 1.86 vs 1.33 ± 2.07; P = .001), and pinch grip strength (0.73 ± 0.63 vs 0.27 ± 0.54; P = .01) than group B. No significant differences in power grip, median compound motor action potential latency, and median sensory nerve action potential latency were seen between the 2 groups.
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Factor analysis of Carpal Tunnel Syndrome Questionnaire in relation to nerve conduction studies

Abstract

Objective

Methods

Results

Conclusions

Significance

Highlights

Introduction

Section snippets

Materials and methods

Demographic characteristics of patients are shown in Table 1

Discussion

J Neurol Sci

Hand Clin

J Hand Surg Am

Diabetes Res Clin Pract

Prevalence of carpal tunnel syndrome in a general population

JAMA

A neurophysiological grading scale for carpal tunnel syndrome

Muscle Nerve

Spanish adaptation of the revised amyotrophic lateral sclerosis functional rating scale (ALSFRS-R)

Amyotroph Lateral Scler

Correlation of electrodiagnostic findings with subjective symptoms in carpal tunnel syndrome

Ann Plast Surg